Ubiquitous WiFi and Acoustic Sensing:Principles,Technologies,and Applications

With the increasing pervasiveness of mobile devices such as smartphones,smart TVs,and wearables,smart sensing,transforming the physical world into digital information based on various sensing medias,has drawn researchers’great attention.Among different sensing medias,WiFi and acoustic signals stand out due to their ubiquity and zero hardware cost.Based on different basic principles,researchers have proposed different technologies for sensing applications with WiFi and acoustic signals covering human activity recognition,motion tracking,indoor localization,health monitoring,and the like.To enable readers to get a comprehensive understanding of ubiquitous wireless sensing,we conduct a survey of existing work to introduce their underlying principles,proposed technologies,and practical applications.Besides we also discuss some open issues of this research area.Our survey reals that as a promising research direction,WiFi and acoustic sensing technologies can bring about fancy applications,but still have limitations in hardware restriction,robustness,and applicability.

Sensorless Sensing with WiFi

Can WiFi signals be used for sensing purpose？ The growing PHY layer capabilities of WiFi has made it possible to reuse WiFi signals for both communication and sensing. Sensing via WiFi would enable remote sensing without wearable sensors, simultaneous perception and data transmission without extra communication infrastructure, and contactless sensing in privacy-preserving mode. Due to the popularity of WiFi devices and the ubiquitous deployment of WiFi networks, WiFi-based sensing networks, if fully connected, would potentially rank as one of the world＇s largest wireless sensor networks. Yet the concept of wireless and sensorless sensing is not the simple combination of WiFi and radar. It seeks breakthroughs from dedicated radar systems, and aims to balance between low cost and high accuracy, to meet the rising demand for pervasive environment perception in everyday life. Despite increasing research interest, wireless sensing is still in its infancy. Through introductions on basic principles and working prototypes, we review the feasibilities and limitations of wireless, sensorless, and contactless sensing via WiFi. We envision this article as a brief primer on wireless sensing for interested readers to explore this open and largely unexplored field and create next-generation wireless and mobile computing applications.

Cross-scene passive human activity recognition using commodity WiFi

With the development of the Internet of Things(IoT)and the popularization of commercial WiFi,researchers have begun to use commercial WiFi for human activity recognition in the past decade.However,cross-scene activity recognition is still difficult due to the different distribution of samples in different scenes.To solve this problem,we try to build a cross-scene activity recognition system based on commercial WiFi.Firstly,we use commercial WiFi devices to collect channel state information(CSI)data and use the Bi-directional long short-term memory(BiLSTM)network to train the activity recognition model.Then,we use the transfer learning mechanism to transfer the model to fit another scene.Finally,we conduct experiments to evaluate the performance of our system,and the experimental results verify the accuracy and robustness of our proposed system.For the source scene,the accuracy of the model trained from scratch can achieve over 90%.After transfer learning,the accuracy of cross-scene activity recognition in the target scene can still reach 90%.